A Zonally-Averaged Stable-Isotope Model Coupled to a Regional Variable-Elevation Stable-Isotope Model

Abstract

A global model is presented that simulates zonal averages of stable isotopes δ(¹⁸O), δ(D) and precipitation rates at sea level. The model is empirical and uses as input zonal averages of evaporation, meridional water-vapour flux, air temperature, sea temperature, wind speed, relative humidity, sea-ice cover, and supersaturation in clouds as a function of temperature. The global model provides input to high-latitude regional solutions that are found integrating up assumed vapour trajectories, which need not be at sea level. Model precipitation rates, δ(¹⁸O) and δ(D), compare well to measured values on an annual and seasonal basis. The stable-isotope-temperature relation poleward of about 35° latitude as well as the isotope-precipitation relation in the tropics is simulated by the zonal global model. The Queen Elizabeth Islands stable-isotope pattern is given as an example of a regional solution of the model. Zonal moisture contributions for high-elevation sites are found to be different between northern hemisphere (Crête, Greenland) and southern hemisphere (Vostok, East Antarctica) with the southern high-latitude cold oceans making a larger relative contribution.